Skeletal Dysplasias TOP TEN THINGS TO KNOW Shawn Parnell, MD Seattle Children’s Hospital University of Washington • Diagnostic tool for evaluating skeletal dysplasias and syndromes • Narrow the DDx, guiding genetic testing and treatment and prognosis Skeletal Survey • AP and Lateral Skull • Lateral Cervical Spine • AP and Lateral Thoracolumbar spine • AP chest • AP Pelvis • AP all extremities (to include hands and feet) • Pearl: Get true lateral view of c-spine (fusion, vertebral shape, odontoid) Skeletal Survey • Sutures • Wormian Bones • Sella Turcica • Craniofacial Proportions • Calvarial/Skull base thickening Skull J-shaped sella J-shaped sella • Alignment • Vertebral Shape • Fusion/Segmentation Anomalies • Interpediculate narrowing lower lumbar spine Spine Nomenclature for abnormal vertebral body shape- lateral view • Normal vertebra • Platyspondyly • Posterior Scalloping • Anterior Beaking • Endplate irregularity • or Nomenclature for abnormal vertebral body shape- lateral view • Anterior Wedging • Normal vertebra • Short Pedicles • Posterior Wedging • Coronal Clefting • Tall Vertebral Body • Normal vertebral column- AP • Decreased interpediculate distance Moving inferiorly in the lumbar spine, pedicles become closer together Narrowing of Interpediculate Distance • Sciatic Notches • Acetabular Roofs • Iliac Wings • Pubic bone ossification Pelvis • Sciatic Notches • Acetabular Roofs • Iliac Wings • Pubic bone ossification Pelvis • Sciatic Notches • Acetabular Roofs • Iliac Wings • Pubic bone ossification Pelvis • Sciatic Notches • Acetabular Roofs • Iliac Wings • Pubic bone ossification Pelvis • Sciatic Notches • Acetabular Roofs • Iliac Wings • Pubic bone ossification Pelvis • Focal or Generalized? • Epiphysis, Metaphysis, Diaphysis? • Small epiphyseal ossification centers • Metaphyseal flaring, marginal irregularity Extremities • Disproportionate shortening • Rhizomelia (proximal) • Mesomelia (middle) • Acromelia (distal) • Micromelia • Polydactyly, duplications, hypoplasia Extremities • Disproportionate shortening of proximal aspect of long bones (humerus, femur) • Achondroplasia Rhizomelia • Most common non-lethal skeletal dysplasia • FGFR3 mutation (also thanatophoric dysplasia, hypochondroplasia) • Abnormal enchondral bone formation Achondroplasia • Skull- Frontal bossing, midface hypoplasia • Spine- Interpediculate narrowing, posterior scalloping, short pedicles • Thorax- Mildly short ribs • Pelvis- Flat acetabular roofs, small sciatic notches, short and wide iliac wings • Extremities- Rhizomelia Achondroplasia Achondroplasia Achondroplasia • Thanatophoric Dysplasia • Jeune Syndrome (Asphixyating Thoracic Dysplasia) Lethal Dysplasias • Similarities with Achondroplasia: • FGFR3 mutations • Pelvis • Narrow foramen magnum • Interpediculate narrowing L spine Thanatophoric Dysplasia Thanatophoric Dysplasia • Differences with Achondroplasia: • Shorter ribs • Micromelia (all portions short) with bent bones • More platyspondyly • LETHAL Thanatophoric Dysplasia Jeune Syndrome Jeune Syndrome • Asphyxiating Thoracic Dysplasia (a.k.a.) • Normal Spine! • Irregular Acetabular Roof (Trident shaped) • No bent bones! • Short ribs! (variably lethal) Jeune Syndrome • “Dysostosis Multiplex” • J-shaped sella (anterior flattening) • Anterior beaking vertebra T-L junction • Proximal pointing metacarpals • Thickened ribs • Narrow inferior portion of iliac bones Mucopolysaccharidoses MPS • Resources: • Textbooks (Taybi and Lachman) • Google groups • Interactive Atlas -Seattle Children’s radiology website (free) • ibook- Little Book of Skeletal Dysplasias (free) • Multidisciplinary conferences (ortho, genetics, endocrine, rads) • [email protected] You are not alone! .